I have been muddling through my first crown molding project and would be happy to share the little I have learned. First of all, I miter both pieces, rather than the technique of straight-cutting one piece and coping the other to fit. 1) I place the molding on the miter saw with the curved face towards me, ceiling surface flat on the base--the molding leans back at a 45 degree angle with the wall surface resting against the back fence. Put the saw miter angle at 45 degrees and cut 2)self-checks that I do throughout the project to make sure each cut is right---the lower edge of the moding should be the long side after the miters are cut. The top edge of the molding (the vertical plane that you will SEE closest to the ceiling should appear with a nice 90 degree cut on that plane, not an angled one. 3)nailing tips--use a square on the back of the molding to get what the vertical measurement should be and make a few pencil marks on the wall accordingly--also keep a short block of scrap to hold up in the corner (hold it up on the adjoining wall where the next piece of molding will go) before final nailing ot make sure that the next piece will line up with the one you're about to nail. I have been predrilling my molding to prevent cracking and trying to nail into the top plate (top of the wall surface) but often miss solid wood--any tips on the nailing?
Hope this was not too confusing and that even these little bits help. Good luck